EG4 Lifepower4 Cell Voltage, Temperature, Overvoltage Questions

[Will Prowse]

A low-cost way to do this is to connect a 48 volt inverter to a dedicated shunt with a watt hour meter. Charge each individual pack to 100% and leave it connected to the charger for a few days. Then connect it to your capacity test system. And then post the results here for everyone to see.

 

[Zapper77]

I was working on this to help other.

This is a rough draft and needs polished. Link to a Word document with photos showing the first 72 hours of top balancing a new set of LP4 batteries

After 20 Hours of Top Balancing.docx

Microsoft Word Document

1drv.ms

 

[sunsurfer]

This is a perfect case study why BMSs should have a top balance "mode" feature built in in addition to the trickle balance they usually have. A simple switch or button would work.

Most users are not going to take the cover off and do a top balance. Most people can barely use a tv remote.

 

[Zapper77]

This is a perfect case study why BMSs should have a top balance "mode" feature built in in addition to the trickle balance they usually have. A simple switch or button would work.

Most users are not going to take the cover off and do a top balance. Most people can barely use a tv remote.

An active balancing BMS would be nice...but you won't find that at the EG4 Lifepower4 price point.

 

[Sundown]

top balancing a new set of LP4 batteries

Is this the cause of 4 cells not charging beyond 3.3V?

 

[Zapper77]

Is this the cause of 4 cells not charging beyond 3.3V?

The 3.3v cells aren't the issue. It's the 3.65v cells. When any cell hits 3.65 the bms shuts off charging. You see the BMS is burning off energy from the higher voltage cells in the Pack.

I estimated that my pack was drawing down .005v per hour while balancing.

So if your cells are .3v higher...you can figure it will take 60 hours to rebalance your pack. BTW bms will only balance a max of 6 cells at any given time.

 

[Will Prowse]

An active balancing BMS would be nice...but you won't find that at the EG4 Lifepower4 price point.

Active balancers are a bad idea. Especially for LiFePO4. Completely unnecessary.

If you are cycling some LTO cells hard, sure. Not for solar with LiFePO4.

 

[Will Prowse]

This is a perfect case study why BMSs should have a top balance "mode" feature built in in addition to the trickle balance they usually have. A simple switch or button would work.

Most users are not going to take the cover off and do a top balance. Most people can barely use a tv remote.

What people should do is cycle the battery. It will fix itself over time. You do not even need to know how to use a tv remote, you just cycle the battery and it will fix itself.

 

[Will Prowse]

The 3.3v cells aren't the issue. It's the 3.65v cells. When any cell hits 3.65 the bms shuts off charging. You see the BMS is burning off energy from the higher voltage cells in the Pack.

I estimated that my pack was drawing down .005v per hour while balancing.

So if your cells are .3v higher...you can figure it will take 60 hours to rebalance your pack. BTW bms will only balance a max of 6 cells at any given time.

Yes exactly. Just keep cycling and it will be fine.

Even with the cell voltage differentials noted in this thread, you can still pull full capacity from day one. So there is no issue. Over a few months of daily cycling, it will balance.

 

[Sundown]

When any cell hits 3.65 the bms shuts off charging. You see the BMS is burning off energy from the higher voltage cells in the Pack.

Doesn't the attached screenshots show there was no OV shutdown and that the bms is still charging/balancing, but those 4 same cells stopped at 3.3V? It has been over 5 months and those same 4 cells never go beyond 3.3V.

Only 6 at a time, correct. As seen in all the screenshots.

I'll add one at 20% SOC, they look great.

 

[Zapper77]

Doesn't the attached screenshots show there was no OV shutdown and that the bms is still charging/balancing, but those 4 same cells stopped at 3.3V? It has been over 5 months and those same 4 cells never go beyond 3.3V.

Only 6 at a time, correct. As seen in all the screenshots.

I'll add one at 20% SOC, they look great.

Switch over to USE setting for a few days, max bulk at 56v. Post again when you reach 56v. I'd like to see the cell data 56v

 

[Zapper77]

Doesn't the attached screenshots show there was no OV shutdown and that the bms is still charging/balancing,

Sure, Maybe...did you cycle the battery on and off?

 

[Sundown]

Switch over to USE setting for a few days, max bulk at 56v. Post again when you reach 56v. I'd like to see the cell data 56v

Been in USE for months. Attached 56V.

 

[Zapper77]

Been in USE for months. Attached 56V.

Do you have anything recent?

 

[Zapper77]

Been in USE for months. Attached 56V.

How did you get the date and time set?

 

[Sundown]

Do you have anything recent?

The one I already posted from yesterday. Charged for 6 hours, no draw, went to float 54.6V.

Here it is:

 

[Sundown]

How did you get the date and time set?

In the BMS Test software with ben's help fromsignaturesolar.

 

[Sundown]

Do you have anything recent?

Is it possible that packs 1/2/3 stop balancing as seen in the screenshot because the Max Diff is <.01V, but packs 4/5/6 keep trying because the cells that won't go beyond 3.3v which keeps the Max Diff average over the BMS cut-off?

 

[Zapper77]

Is it possible that packs 1/2/3 stop balancing as seen in the screenshot because the Max Diff is <.01V, but packs 4/5/6 keep trying because the cells that won't go beyond 3.3v which keeps the Max Diff average over the BMS cut-off?

Is it possible that packs 1/2/3 stop balancing as seen in the screenshot because the Max Diff is <.01V, but packs 4/5/6 keep trying because the cells that won't go beyond 3.3v which keeps the Max Diff average over the BMS cut-off?

What are your charge settings, bulk voltage, time before float and float voltage?

 

[LithiumCowboy]

How did you get the date and time set?

The new version of BMS Test V2.7 on the eg4electronics website now has a time/date update in the ConfigInfo tab.